I'm trying to solve for Mach number based on the given Prandtl-Meyer function, however I keep getting odd error.

Here is my code:

g = 1.4

v2 = 54

Solve[v2 == (Sqrt[(g + 1)/(g - 1)]*
        ArcTan[Sqrt[(g - 1) (M2^2 - 1)/(g + 1)]] - 
       ArcTan[Sqrt[M2^2 - 1]])/Pi*180, {M2}];

This is the website that has the function I'm trying to solve.

Any help would be greatly appreciated.

##UPDATED:

g = 1.4

v2 = 54.76

M2 := FindRoot[
  v2 == (Sqrt[(g + 1)/(g - 1)]*
        ArcTan[Sqrt[(g - 1) (x^2 - 1)/(g + 1)]] - 
       ArcTan[Sqrt[x^2 - 1]])/Pi*180, {x, 3}]
M2